I agree entirely, I love Lolita even though Humbert disgust me because I don't have to relate to the protagonist to enjoy reading. And I think most real humans are morally ambiguous at some point or another, so characters without deep flaws are unrealistic and poor writing.

I agree with everything you said, actually, "challenge our perspectives..." which is exactly the point of good literature, beyond entertainment, it forces us to confront unpleasant realities, and by proxy, ourselves.